The correct answer is that the lease time is set to 7 days, causing old devices to hold IP addresses long after disconnecting. This leads to DHCP pool exhaustion because the router’s pool for the 192.168.1.0/24 subnet shows 253 current bindings out of 254 total addresses, leaving only one free IP. With a lease expiration of seven days, devices that have left the network still retain their bindings for a full week, preventing new clients from obtaining an address and forcing them to fall back to APIPA. On the CCNA 200-301 v2 exam, this scenario tests your understanding of how lease duration directly impacts address availability; a common trap is to overlook the lease time and blame the subnet mask or a rogue DHCP server. Remember the memory tip: “Long lease, slow release” — if the lease is too long, old clients hog addresses, and new ones get APIPA.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
R1# show ip dhcp pool
Pool LAN-POOL :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 254
Leased addresses : 253
Excluded addresses : 0
Pending events : 0
Subnet : 192.168.1.0/24
Current bindings : 253
Lease expiration : 7 days 0 hours 0 minutes
Automatic bindings : 253
Manual bindings : 0
Conflict reservations : 0
Refer to the exhibit. A network administrator notices that newly connected devices on the 192.168.1.0/24 subnet are failing to obtain IP addresses via DHCP and are instead assigning themselves APIPA addresses. The administrator issues the show ip dhcp pool command on the router and receives the output shown. What is the most likely cause of this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
R1# show ip dhcp pool
Pool LAN-POOL :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 254
Leased addresses : 253
Excluded addresses : 0
Pending events : 0
Subnet : 192.168.1.0/24
Current bindings : 253
Lease expiration : 7 days 0 hours 0 minutes
Automatic bindings : 253
Manual bindings : 0
Conflict reservations : 0
A
DHCP snooping is blocking DHCP Offer messages on the VLAN.
Why wrong: The output does not mention DHCP snooping, and no evidence (e.g., dropped packets) suggests filtering. The issue is clearly a depleted pool.
B
The DHCP pool has an address conflict, causing all addresses to be marked as ineligible.
Why wrong: The exhibit shows 'Conflict reservations: 0', proving no conflicts exist. Conflicts would not cause 253 bindings out of 254.
C
The lease time is set to 7 days, causing old devices to hold IP addresses long after disconnecting.
The 'Lease expiration' of 7 days combined with 'Current bindings: 253' reveals that the pool stays exhausted because leases take a week to expire, starving new clients of addresses.
D
The pool's subnet mask is incorrectly configured as /24 instead of /25, limiting available addresses.
Why wrong: A /24 mask provides exactly 254 usable host addresses, matching the 'Total addresses: 254' shown. Changing to /25 would cut the pool to 126 addresses and make the problem worse.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The lease time is set to 7 days, causing old devices to hold IP addresses long after disconnecting.
The exhibit shows 'Current bindings: 253' out of 'Total addresses: 254', meaning only one free IP remains. 'Lease expiration' is 7 days, indicating that devices that have disconnected still hold their bindings for up to a week, preventing new clients from obtaining addresses. This explains the APIPA fallback.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
DHCP snooping is blocking DHCP Offer messages on the VLAN.
Why it's wrong here
The output does not mention DHCP snooping, and no evidence (e.g., dropped packets) suggests filtering. The issue is clearly a depleted pool.
✗
The DHCP pool has an address conflict, causing all addresses to be marked as ineligible.
Why it's wrong here
The exhibit shows 'Conflict reservations: 0', proving no conflicts exist. Conflicts would not cause 253 bindings out of 254.
✓
The lease time is set to 7 days, causing old devices to hold IP addresses long after disconnecting.
Why this is correct
The 'Lease expiration' of 7 days combined with 'Current bindings: 253' reveals that the pool stays exhausted because leases take a week to expire, starving new clients of addresses.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
The pool's subnet mask is incorrectly configured as /24 instead of /25, limiting available addresses.
Why it's wrong here
A /24 mask provides exactly 254 usable host addresses, matching the 'Total addresses: 254' shown. Changing to /25 would cut the pool to 126 addresses and make the problem worse.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The lease time is set to 7 days, causing old devices to hold IP addresses long after disconnecting.Correct answer▾
Why this is correct
The 'Lease expiration' of 7 days combined with 'Current bindings: 253' reveals that the pool stays exhausted because leases take a week to expire, starving new clients of addresses.
✗DHCP snooping is blocking DHCP Offer messages on the VLAN.Wrong answer — click to see why▾
Why this is wrong here
Candidates often prematurely blame security features when DHCP fails, ignoring the pool statistics right in front of them.
✗The DHCP pool has an address conflict, causing all addresses to be marked as ineligible.Wrong answer — click to see why▾
Why this is wrong here
A common mistake is assuming that conflicts always fill up a pool, but the zero value directly disproves this.
✗The pool's subnet mask is incorrectly configured as /24 instead of /25, limiting available addresses.Wrong answer — click to see why▾
Why this is wrong here
Misunderstanding subnet sizing often leads candidates to blame the mask, but the exhibit confirms the mask is appropriate for the pool size.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Trap categories for this question
Command / output trap
The output does not mention DHCP snooping, and no evidence (e.g., dropped packets) suggests filtering. The issue is clearly a depleted pool.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
Network Services and Security — This question tests Network Services and Security — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The lease time is set to 7 days, causing old devices to hold IP addresses long after disconnecting. — The exhibit shows 'Current bindings: 253' out of 'Total addresses: 254', meaning only one free IP remains. 'Lease expiration' is 7 days, indicating that devices that have disconnected still hold their bindings for up to a week, preventing new clients from obtaining addresses. This explains the APIPA fallback.
What should I do if I get this 200-301 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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